In addition to the usual hemodynamic and blood gas measurements currently being made in the critically injured patient, a series of additional metabolic studies will be simultaneously performed. These will include the continuous measurement of oxygen consumption, carbon dioxide production, and carbon 14 dioxide production. Plasma amino acids will be serially studied as well as glucose, lactate, pyruvate, acetoacetate, and beta hydroxybuterate. In addition plasma levels of glucagon, insulin, growth hormone, and cortisol will be determined in portal vein and hepatic vein blood in animals and later in patients, when this becomes possible.